Components that are exposed to extreme temperatures such as those in a combustion gas path in a gas turbine engine are typically provided with a protective ceramic coating. The coating can include a multiple layers that are built up on the part.
As the components and the protective coating are exposed to thermal cycles (e.g., during operation of the gas turbine engine) the layers forming the coating experience significant amounts of thermal and mechanical stress. The layers may each have a different modulus of elasticity or undergo different rates of thermal expansion. This can cause the connections between each layer to fail or cause cracks to form in the coating. These cracks can propagate through the coating and cause spallation of the coating from the part. Additionally, an oxide layer can grow between the layers of the coating. Growth of the oxide layer can also affect the connection of the layers and cause further spallation of the coating from the part.
There is, therefore, a need for a coating that improves the connection between the layers forming the coating and slows propagation of cracks through the coating.